WO2011/071912, WO2012/057878, and WO2014/144782 present systems and methods for separating microparticles or cells within a ferrofluid medium using magnetic forces. Magnetic field excitations can sort, separate, focus, and even capture cells and other microparticles.
Mechanical exclusion, via well-known filtration is, by its very nature, prone to clogging, and also subsequent increases in pressure drop across the filter as the filter becomes more and more clogged. Such filtration means rely on physically stopping a large enough target particle across a smaller opening on a surface. Additionally, diffusion on traditional assays is slowed by speed limitations. For example, in traditional immunoassays, multiple time-consuming and labor-intensive wash cycles are required between steps.